Takaya Terada

Determination of the tumor tissue optical properties during and after photodynamic therapy using inverse Monte Carlo method and double integrating sphere between 350 and 1000 nm

Photodynamic therapy (PDT) efficacy depends on the amount of light distribution within the tissue. However, conventional PDT does not consider the laser irradiation dose during PDT. The optical properties of biological tissues (absorption coefficient μ(a), reduced scattering coefficient μs), anisotropy factor g, refractive index, etc.) help us to recognize light propagation through the tissue. The goal of this paper is to acquire the knowledge of the light propagation within tissue during and after PDT with the optical property of PDT-performed mouse tumor tissue. The optical properties of mouse tumor tissues were evaluated using a double integrating sphere setup and the algorithm based on the inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. During PDT, the μ(a) and μs were not changed after 1 and 5 min of irradiation. After PDT, the μs in the wavelength range from 600 to 1000 nm increased with the passage of time. For seven days after PDT, the μs increased by 1.7 to 2.0 times, which results in the optical penetration depth decreased by 1.4 to 1.8 times. To ensure an effective procedure, the adjustment of laser parameters for the decreasing penetration depth is recommended for the re-irradiation of PDT.

High Gradient Superconducting Magnetic Separation for Iron Removal From the Glass Polishing Waste

Cerium oxide used for glass polishing agent is processed as wastewater mixed with the polishing sludge of the glass. The recycling of cerium oxide may have a large influence on reduction of environmental burden and resources recycling. In the treatment process of wastewater, the complex of cerium oxide and iron flocculant is formed by co-precipitation to clear the fluid. In order to recycle the cerium oxide, it is necessary to eliminate the cohesion and then remove the iron content. In this study, the aggregated particles were dispersed by pH adjustment, and the iron content was separated by the developed high gradient magnetic separation system (HGMS) with superconducting magnet. The optimum condition was examined by calculation and experiment. In addition, we succeeded to remove the silica particle by magneto-Archimedes levitation. It was confirmed that ferrous particles and silica particles can be removed from wastewater by using superconducting bulk magnet, which makes it possible to reuse ceria particle as the polishing agent.

Research and Development of Superconducting Magnetic Separation System for Powdered Products

The superconducting magnetic separation system which separates ferromagnetic particles from powder mixture has been developed. It is required to remove the impurities from the powdered products without using chemical or heating processing. The impurities are usually powdered stainless steel from the piping which are deformed strongly and shows ferromagnetism. Magnetic separation using permanent magnets have been used for the separation. The conventional magnetic separation system has not shown the expected performance especially for the small sized impurities. To solve the problem, superconducting magnetic separation system was developed. We used the magnet with magnetic field up to 2 T. The boa size was 100 mm in diameter. Inside of the magnetic boa the magnetic filters are located to produce the high magnetic gradient. The performance of the separator was reported together with the design guideline.

High-Speed Magnetic Filtration System Using HTS Bulk Magnet for Used Wash Water of Drum

Fundamental study of a high speed filtration system using HTS magnet for purifying the used wash water of drum has been made. This system consists of a magnetic seeding device and a magnetic filtration device. Since the wastewater is a mixture of various used wash water, the wastewater treatment is difficult to realize practically. For that reason, the wastewater is processed as industrial waste products. In the purification system the waste component in the wastewater is made into the floc containing magnetite in the magnetic seeding device. The wastewater is made to flow close to HTS bulk magnet and the floc is filtered by magnetic force. It was found that the system shows the extensibility and is low cost because of the simple construction.

Determination of optical property changes during laser therapies

Optical property changes should be considered to realize safe laser treatments. This study shows the optical properties of normal and laser treated tissues in visible to near-infrared wavelength range by using double integrating sphere system.

Error analysis of tissue optical properties determined by double-integrating sphere system and inverse Monte Carlo method

To estimate the error of scattering coefficient spectrum determined by using double-integrating sphere system and inverse Monte Carlo method, optical properties of tissue phantom were measured. The tissue phantom was composed of hemoglobin, intralipid and gelatin. The thickness of samples (0.1-1.0 mm) and hemoglobin concentration (0.5-4.0 mg/ml) were changed and the effects of optical properties spectra were investigated. As the results, when the value of μa was large, μs spectrum was not consistent with scattering theory. The higher hemoglobin concentration of samples was the lager the errors of μs spectra were. The thinner the sample was, the smaller the errors were. However μa spectrum was not accurate when the sample was thin. It was predicted that when the sample thickness was 0.1 mm μs spectrum was accurate. And when the sample thickness was 1.0 mm, μa spectrum was accurate.

Determination of the optical property changes by photodynamic therapy using inverse Monte Carlo method between 350 nm and 1000 nm

The clinical outcome of photodynamic therapy (PDT) may be improved by the accurate knowledge about the light distribution within the tissue. Optical properties [absorption coefficient (μa), scattering coefficient (μs), anisotropy factor (g), refractive index, etc.] of tissues help us realizing a light propagation through the tissue. The aim of this study is acquisition of the knowledge of light propagation within tissue with the optical property of mouse tumor tissue performed PDT. We evaluated the optical property of mouse tumor tissue before and after PDT using the double integrating sphere setup and algorithms based on the inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. During PDT, the reduced scattering coefficient spectra were decreased entirely after 5 and 10 min irradiation. 1, 2, 7 days after PDT, the absorption coefficient was increased in the wavelength range from 400 to 660 nm. And, the reduced scattering coefficient at the wavelength of 664 nm was increased with the passage of time. These results are used for medical diagnostic applications for the quantitative assessment of the PDT effect. 7 days after PDT, the reduced scattering coefficient at the wavelength of 664 nm was increased significantly from 0.64 mm-1 to 1.24 mm-1, which results in the optical penetration depth decreased from 1.49 mm to 0.84 mm, respectively. To ensure the effective procedure, an adjustment of the laser parameter for the decreasing penetration depth is recommended for a second PDT.